Isomerization of normal paraffin hydrocarbons



E. E. sENsEl. ET AL 2,419,423

`ON OF NORMAL PARAFFIN HYDROCARBONS April 22, 1947.

ISOMERIZMI Filed June 50. 1959 EUGENE E. SENSEI.

.SSR @$3.36

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Patented Apr. 22, .1947

ISOMERIZATION F NORMAL PARAFFIN HYDRO CARBON S Eugene E. Sensel, HaroldV. AtwelLand Arthur R. Goldsby, Beacon, N. Y., assignors, by mesneassignments, to The Texas Company, New York,

y N. Y., a corporation of Delaware Application June 30, 1939, Serial No.282,054

3 Claims.

This invention relates to the conversion of hydrocarbons and has to dowith the isomerization of normal parains to isoparafns. It is applicableparticularly with respect to the isomerization of normal butane toisobutane.

A continuous method ofy isomerizing normal paran hydrocarbons,particularly normal butane, involves subjecting the normal paraffinhydrocarbon, in the liquid phase, to contact with an anhydrous aluminumhalide catalyst and a hydrogen halide promoter at temperatures of about150 to 275 F., whereby the isoparaiiin hydrocarbon is formed.

The present invention involves saturating the hydrocarbon feed in suchan isomerization process with thecatalyst Lat approximately the conversion temperature, .The hydrocarbon feed, saturated with the catalystand in liquid phase, is passed through a reaction zone wherein it isbrought into contact with the catalyst, whereby isoparain hydrocarbonsare formed. v

` The hydrocarbon mixture leaving the reaction zone. is diluted withanvadditional quantity of normal paraflin or paraflin-isoparain mixtureandthe dilute `mixture passed to a fractionating zone. The fractionationVis regulated so as to produce a vapor fraction comprising isoparaffinhydrocarbons which is removed.

The bottoms from the fractionation comprise unreacted normal parainhydrocarbons in liquid form containing dissolved catalyst. These arerecycled to the saturating and isomerizing zones.

It is contemplated eiecting the conversion with the catalyst, such asanhydrous aluminum chloride, in the presence of an. anhydrous hydrogenhalide, such as hydrogen chloride. The promoter may be mixed with thehydrocarbon feed subsequent to saturating with the catalyst.

The reaction is carried on under superatmospheric pressure sufficient tomaintain the parafn hydrocarbons in the liquid phase. The pressure willdepend upon the temperature used and, in the case of normal butane, willvary from 150 to 500 pounds per square inch. The temperature may rangefrom 150 to 275 F. and is preferably around 200 to 250 F.

In order to illustrate the invention further reference is made to theaccompanying drawing, which shows diagrammatically methods of dowadapted for carrying out the invention:

As shown in Fig. 1, the hydrocarbon feed comprising, for example, normalbutane, or a mixture consisting predominantly of normal butane, isconducted from a source not shown through a pipe I, andby means of apump 2 passed under (Cl. 26m-683.5)

pressure and in liquid phase to a purifying vessel 3, or a series ofsuch vessels, wherein the butane is agitated or contacted with sulphuricacid or other chemical agent or mixture, such as aluminum chlorideadmixed with hydrogen chloride, in order to remove olens and otherundesired compounds. In the event that the normal butane charged is freefrom olens and other undesirable compounds, the purifying step may beomitted. The puriiied butane, or a mixture Consisting primarilyof normalbutaney is transferred from the purier 3 through a pipe 4 to a preheater5, wherein it is raised to the desired temperature, which may beapproximately equal to, or slightly above, the temperature of conversionprevailing in the'subsequent isomerization step.

From the preheater Sthe normal butanevpasses through a saturatingvesselB. The vessel 6 may be provided with means for heating or formaintaining the temperature at the' desired elevation. Anhydroushydrogen chloride may `be introduced to the 'vessel 6 through a pipe 1.The vessel .6 contains aluminum chloride or other aluminum halides withwhichto saturate the butane. During passage through the vessel 6 thebutane becomes saturated with the catalyst and the saturated mixture isdischarged therefrom through a pipe 8 to a reaction vessel 9. Vesselralso serves as an additional purifier for the butane feed; serving toremove any pentanes or higher hydrocarbons resulting from recycling orintroduced with the fresh feed.

The reaction Vessel 9 may conveniently take the formof a vertical towerand contains the catalyst in solid or lump form. If desired, thecatalyst may be deposited on an inert support, e. g., alumina, clay,pumice, coke, brick, etc. As indicated, the catalyst may be disposed ina series of beds one above the other within the tower.

4The vessel 9 is operated at any desired 'temperature in order -toaccomplish substantial isomerization of normal butane to isobutane.Although upward ow of the hydrocarbon feed through the reaction vessel 9is indicated, it is contemplated that downward flow may be employed, ifdesired.

Additional promoter or the entire feed thereof may be introduced to thereaction vessel 9 by means of a pipe l0, the promoter being mixed withthe hydrocarbon mixture passing to the vessel 9.

While a portion of the promoter may be introduced prior to passagethrough the saturator 6,

it iscontemplated that all, or substantially all, of

the promoter may be added to the hydrocarbon 3 mixure subsequent topassage through the vessel The products of isomerization comprisingessentially normal butano and isobutane, still saturated with aluminumchloride and containing hydrogen chloride promoter, are transferred fromthe top of the vessel Q through a pipe II to a manifold I2, providing ameans of introduction to a fractionating tower I3.

An additional quantity of normal butano. or fresh charge containingprimarily normal butano, is mixed with the isomerized products prior tointroduction to the fractionating tower I3. This additional butano isintroduced through a pipe Ill, communicating with pipe previouslymentioned.

The amount of normal butano, or fresh charge consisting primarily ofnormal butano, added as a diluent preferably corresponds in volume toap'- proximately the amount of isobutane contained in the products ofisomerization. It should bo sufficient to retain the catalyst insolution within the fractionator I3 upon removal of the isobutane fromthe hydrocarbon mixture entering the fractionator.

The purpose of this additional butano is to avoid deposition of theYcatalyst in solid form upon the bubble trays within the fractionator.

Pipe II, manifold I2, and tower I3 are maintained at the sametemperature as that prevailing in the reaction vessel 9, or even at aslightly hi-gher temperature in order to prevent precipitation fromsolution of aluminum chloride.

The fractionator I3 is operated so as to remove, through pipe I5, avapor fraction comprising isobutane. This fraction will contain hydrogenchloride and may contain some normal butano. It is passed to a condenserI6, wherein it is cooled, and from there it passes to an accumulator Il.Hydrogen chloride may be removed directly from the top of thefractionator through a pipe communicating with a pipe 22 to whichreference will be made later.

rIhe pressure in the fractionating tower I3 is maintained constant bymeans of a valve I0, While the pressure in the accumulator II ismaintained by a valve I9.

A portion of the liquefied isobutane fraction collecting in theaccumulator l1 is withdrawn by means of a pump and returned to the upperportion of the fractionator I3 as a reiiux.

The surplus isobutane liquid is drawn on from the accumulator through apipe ZI and may be subjected to such further treatment as desired, inorder to remove and recover any hydrogen chloride contained therein.

The hydrogen chloride, hydrocarbons lighter than isobutane, and fixedgases from the accumulator Il are drawn of through the valve I9 andrecycled through a pipe 22 to a compressor 23, wherein they arecompressed. In this way certain of the hydrocarbons are liquefied. Thecompressed and liquefied gases pass through a heat exchanger 24 to anaccumulator 25.

The fixed gases, together with a portion of the gaseous hydrogenchloride, are periodically released through a valve 2li to an auxiliarysystem not shown, where the hydrogen chloride may be recovered, ifdesired.

Hydrogen chloride from the recovery system is introduced through a pipe27 which communicates with pipes I0 and I previously referred to.Further, the liquefied hydrocarbons containing dissolved hydrogenchloride may be charged through line 2l to pipes I0 and l, to therebyrecycle directly a portion of the hydrogen chloride.

Referring again to the fractionator I3, the nor'- mal butano, or butanocontaining fraction, which is introduced through the pipe lli fordiluting the isomerized products, may be heated in a separate zone notshown before it enters the pipe I I. The butanes coming from thereaction vessel 9 are saturated with aluminum chloride at thetemperature prevailing within the vessel 9, As the stream ci freshnormal butano, or mixture comprising essentially normal butano, frompipe I4 mixes with the solution in pipe II, the resulting mixturebecomes less concentrated with respect to aluminum chloride. When themixture enters the ractionator I3 and is subjected to fractionation, thenormal butano, or butano containing fraction, which was introducedthrough pipe I4, dissolves that aluminum chloride which Would otherwisedrop out of solution from the isobutane as the latter proceeds in thegaseous form upward through the fractionator in the process offractionation. In this manner the aluminum chloride is prevented fromprecipitating out in the solid phase.

The solution of aluminum chloride in normal butano and any heavierhydrocarbons in the fractionator I3 proceeds downwardly and is withdrawnby a pump 30 and transferred to a reboiler 3l.

The material vaporizod in the reboiler 3I is returned to tho lowerportion of the fractionator i3 through a pipo 33.

The excess and unvaporized liquid from the bottom of the fractionator I3and from the reboiler Si is withdrawn by means of a pump 34 andconducted, all or in part, through a pipe 35 to the saturator 6. Ifdesired, it may be recycled directly to the reaction vessel 9 through apipe 36. That portion not returned either to the saturator c or thereaction vessel S is drawn oi from the system through a pipe 31.

Any catalyst or catalyst complex accumulating in the lower portion ofvessel 9 can be discharged through a pipe 42 into the saturator 6. Also,used catalyst discharged from any of the trays of tower 9 can beemployed in saturator On the other hand, the saturator 6 may be chargedwith fresh catalyst.

The process as described above is not limited to the uso of aluminumchloride as a catalyst. The method can be app-lied with any normalbutano isomerization catalyst which is soluble in the butanes, namelyaluminum bromide and aluminum iodide. Aluminum bromide has severaladvantages, one of which is a low melting point (197 F.) which makes itpossible to handle it as a liquid in properly heated lines andapparatus. Aluminum bromide can be distilled as a liquid at atmosphericpressure in contrast to aluminum chloride which sublimes at atmosphericpressure at 352 F. without previous fusion.

Mixtures of catalysts can be used, e. g., mixtures comprising two ormorel of the following: Aluminum chloride, aluminum bromide, and.aluminum iodide. The catalyst is employed in an anhydrous condition.

Anhydrous hydrogen halides 'are used as promoters singly or in mixtures,with themselves or other promoters. Hydrogen chloride, hydrogen bromide,hydrogen iodide, and hydrogen fluoride are contemplated. The percentageVof promoter added may be around 0.1 to 20% by weight of the butanocharged, although from 0.5 to 2% is proferred.

The contact time in the vessel 9 may vary from a few minutes to' an houror more, depending upon the percentage conversion to isobutane desiredand other operating conditions.

It is contemplated that the process is applicable to the isomerizationof hydrocarbonsbther than normal butane, as, for example, normalpentane,

, naphtha and various fractions thereof, etc,

- As indicated in Fig. 2, the products of isomerization leaving the topof the vessel 9, through the pipe II, instead of being passed directlyto the fractionatoi` I3, are passed through a pipe 58 communicating withvessels 5 and 6 through a pipe manifold adapted to provide a pluralityof points of introduction to the vessels B and The pipe connections aresuch that the stream from pipe 50 can be alternated from one vessel tothe other.

The vessels 5 and 6 may be equipped with agitating means, if desired.'Ihey are provided with a. plurality of coils 5i, through which acooling or heating medium may be passed as desired.

In operation the products of isomerization passing through the pipe 553are introduced, for example, to the lower portion of the vessel Si', theinterior of which is maintained at a temperature of around 150 F. orthereabouts by circulating a cooling medium through the lower coils. Theproducts of isomerization are thus reduced in temperature within thevessel S', which causesv precipitation of a portion of the dissolvedaluminum chloride.

The partially cooled liquid products pass upwardly through the vessel 6and are discharged therefrom through pipe 52 communicating with pipemanifold I2, previously referred to in the discussion of Fig. l andwhich provides a means of introduction to the fractionating tower i3.After introduction through the manifold I2 the hydrocarbons aresubjected to fractionation within the fractionator i3 in a mannersimilar t0 that already described in connection with Fig. 1.

When the vessel 6 is substantially iilled to capacity with precipitatedaluminum chloride, the flow of iscmerization products through pipe 5D isdiverted from the vessel 6 to the vessel B, which is in turn cooled tocause precipitation and deposition of aluminum chloride within thevessel. Similarly, the cooled isomerization products from the vessel 5pass through pipe 52 to the fractionator I3.

When the vessel E is being used as a precipitator in which aluminumchloride is being dee posited, the vessel S', previously lled withprecipitated aluminum chloride, is used as a saturator. Thus, theincoming hydrocarbon feed to the tower 9 from the heater 5 is passedupwardly through the vessel E. During this time the vessel 6 ismaintained at about the same temperature as that prevailing in thereaction vessel 9, or even at a somewhat higher temperature. The desiredtemperature may be maintained by passing steam through the coils 5lwithin the vessel 6.

It is, of course, contemplated that paraffin hydrocarbons being recycledthrough the system may also pass through whichever of the vessels 6 and6 is being used as a saturator.

The hydrocarbon feed, after passage through v catalyst to the top of thetower.

the saturating vessel, is discharged therefrom through a pipe 53communicating with pipe 1 ypreviously referred to in the discussion ofFig. 1 and which provides aY means of introduction of hydrocarbon feedto the vessel 9.

When the vessel t has become filled with deposited aluminum chloridethen the iiow of uids is reversed so that the fresh feed hydrocarbonspass through the vessel il, while the isomerization products passthrough the vessel 6. As indicated, hydrogen chloride may be introducedby line It to the line leading from the vessels 6 and Ei' to the vessel9, as already described in connection with Fig. 1.

Additional aluminum chloride may be added periodically to the vessels 6and 6 to replace any catalyst that is converted into complex compounds,with the hydrocarbons, or otherwise, rendered inactive during theprocess.

As already mentioned, the hydrocarbons may be introduced to the vessels6 and Il at a plurality of points, so that the isomerization productsfrom the vessel 9 may be progressively introduced at higher levels asthe vessels become lled to higher levels with precipitated catalyst, dueto the cooling of the products within the vessel. Provision may be madefor conning the flow of cooling water iirst to the lower coils of thevessel, and as this portion of the vessel fills with catalyst thecooling water is introducedto successively" higher coils, while at thesame time the isomerization products are likewise introduced atcorrespondingly higher levels.

Fig. 3 illustrates a method of operating the reaction vessel 9 whenusing aluminum bromide as thel catalyst in molten form. The vessel 9 ispacked with suitable packing material, such as flint, Raschig rings,etc., adapted to facilitate distribution of the uids within the towerand to provide contact between the hydrocarbons rising through the towerand the molten catalyst flow-r ing downwardly therethrough.

The hydrocarbon feed is introduced to the tower at a point below thelower bed of-packing material through a pipe Gil.

A body of molten catalyst accumulates in the bottom of the vessel 9 andis drawn off through a pipe 6I by a pump 52, which returns the molten Inthe top of the tower there is provided .a spray or distributor E3, whichdistributes the returning catalyst over the packing material.

The isomerized hydrocarbon-s are drawn off from the top of the towerthrough the pipe II, as described in connection with Figs. 1 and 2.

`Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritland scope thereof, and therefore only such limitations should beimposed as are indicated in the appended claims.

We claim:

1. In a continuous process of subjecting nor'- mal paraffin hydrocarbonsto contact with an active metallic halide isomerization catalyst duringpassage in liquid phase through primary and secondary zones of contactwith the catalyst at a temperature within the range of to 275 F. toeffect substantial conversion to isoparaflins, and such that a portionat least of the catalyst in the secondary zone forms metallichalidehydrocarbon complex, the steps comprising passing the hydrocarbonfeed to said primary zone, subjecting the feed to intimate contact inthe primary zone with active metallic halide including complex formed insaid secondary zone at approximately the conversion temperature,passfrom the secondary zone, removing the complex formed in saidsecondary zone and passing it by gravity to said primary zone forcontact With fresh hydrocarbon feed.

2. In a continuous. pro-cess oi subjecting normal parafns to Contactwith aluminum chloride and a small amount of hydrogen chloride duringpassage in liquid phase through primary and secondary zones of contactwith the catalyst, at least a portion of the catalyst in the secondaryzone forming aluminum chloride-hydrocarbon compleX, the steps comprisingpassing a hydrocarbon feed containing mainly normal butane to saidprimary zone, subjecting the feed to intimate contact therein withactive aluminum chloride including complex formed in said secondary Zoneat a temperature in the range 150 to 275 F., passing the treatedhydrocarbons from the primary Zone to the secondary zone arranged at anelevation above said primary zone, subjecting the hydrocarbons in thesecondary zone to intimate contact with relatively fresh aluminumchloride conned therein in solid form at a temperature within theaforesaid range, such that substantial conversion to isoparailin occurs,removing the treated hydrocarbons from the secondary zone, removing thecomplex formed therein, and passing the removed complex by gravity tothe primary zone for Contact with fresh hydrocarbon feed.

3. In the continuous catalytic isomerization ofnormal butano in thepresence of an aluminum chloride catalyst and hydrogen chloridepromoter, wherein a fresh feed consisting predominantly of normal butanois preheated to a temperature of about 150 to 275 F. and passed inliquid phase in contact with solid aluminum chloride in the absence ofadded hydrogen chloride in a saturating step to dissolve aluminumchloride, then the preheated normal butano feed containing` dissolvedaluminum chlori'de is passed in liquid phase through an isomerizing Zonecontaining aluminum chloride catalyst and added hydrogen chloridepromoter under isomerizing conditions including a temperature of about150 to 275 F. eiective to convert a substantial proportion of the normalbutane to isobutane with the production of a small amount ci pentane,and a stream of hydrocarbon reaction products containing hydrogenchloride is continuously discharged therefrom, the improvement Whichcomprises fractionating; the said discharged stream to separatetherefrom (1)- a lgl-iterv vapor fraction comprising hydrogen chloride,(2) an isobutane fraction Which is discharged as a final product, and(3) a heavier fraction consisting predominantly of normal butane ireefrom hydrogen chloride and containing a small amount of pentane,recycling at least a portion of said heavier fraction to the saturatingstep whereby pentane is removed therefrom and the puried recycle normalbutane dissolves aluminum chloride in the absence of hydrogen chlorideand is passed with fresh feed to the isomerizing Zone, and recyclinghydrogen chloride from fraction (l) and introducing the same into thefresh and recycle normal butane feed containing dissolved aluminumchloride passing from the saturating step to the isomerizing zone sothat the hydrogen chloride recycle is mixed With the freshl and recyclenormal butano feed subsequent to the said saturating step and prior tointroduction into the isomerizing zone.

EUGENE E. SENSEL. HAROLD V. ATWELL. ARTHUR R. GOLDSBY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,169,494 Ipatieif et al. Aug.15, 1939 1,665,406 Danckwardt Apr. 10, 1938 2,198,595 Amos et al Apr.30, 1940 1,373,653 -Danckwardt Apr. 5, 1921 1,381,098 Alexander et alJune 14, 1921 1,620,075 Clancy Mar. 8, 1927 1,716,372 Downs June 11,19219 1,872,446 Halloran et al Aug. 16, 1932 2,071,521 Hartmann et al.Feb. 23, 1937 2,220,092 Evering Nov. 5, 1940 2,266,011 dOuville et al.(A) Dec. 16, 1941 2,266,012 dOuville et al. (B) Dec. 16, 1941 2,347,266Ipatieff et al Apr. 25, 1944 FOREIGN PATENTS Number Country Date 498,463British Jan.,5, 1939 498,512 British Jan. 5, 1939 823,595 French Jan.22, 1928 Y OTHER REFERENCES Glasebrook et al., J. A. C. S. 58, 1944-48,(1936) Moldavskii et al., J. Gen. Chem. (USSR) 5 1791-97 (1935).

Petrov et al., on a Gas J., Feb. 2, 1939, pp. 42 and 46.

Ipatiei et al.,

Jor. Ind. Eng. Chem., vol. 28, 461-4. Y

